It is common for vehicle engines to drive a plurality of accessories using an accessory drive system that includes a belt. In some vehicles, a motive device is provided such as a motor/generator unit (MGU) that can be used for a number of purposes, such as, for example, driving one or more accessories via the belt when the engine is temporarily off while the vehicle is stopped for a short period of time (e.g. at a stoplight). Another purpose is for use as part of a belt alternator start (BAS) drive system wherein the MGU is used to start the engine through the belt. Another purpose is to supply additional power to the engine when needed (e.g. when the vehicle is under hard acceleration). In such situations special tensioning devices are typically needed to ensure that the belt is under the appropriate amount of tension regardless of whether it is being driven by the MGU or by the engine. In many instances however such tensioning devices are not optimal and result in relatively high belt tensions and hub loads on the various pulleys in the system, thereby negatively impacting fuel economy and component life.
It would be desirable to provide a tensioning system that at least partially addresses one or more of the problems described above and other problems.